XCOM for AS400 random incoming transfer failures

Products

• XCOM Data Transport

Issue/Introduction

This is a repetitive transmission daily.
It runs several times each day and most times completes successfully. There have just been two such failures over the last week, see the detail below:

2 job logs are provided:
In job log #1 with the issue is this error:
Message . . . . :   Space offset X'00000000' or X'0000800070015C90' is outside                 
                                       current limit for object SSL4S08045XCOM      580859.  

Job log #2 is an example of a normal run.

Environment

CA XCOM r11 (IPv6) GENLVL 1707 SP02
OS: v7r4
CUMULATIVE PTF PACKAGE C3117740 (level 23117)

Resolution

Engineering reviewed the 2 job logs.

Although job log #2 appears to be normal and does not report an error it is not an XCOM transfer.

Job log #1 shows a machine check MCH0601 (abend):
Message . . . . :   Application error.  MCH0601 unmonitored by CAXC2SSL at                     
                                       statement 0000000076, instruction X'0000'. 

That MCH0601 happens before the SSL handshake is completed and it looks similar to job log #2 i.e. it is not an XCOM transfer.

It was confirmed that the remote IP address values in both logs were related to a Qualys server i.e. Qualys is doing port scans of the XCOM SSL port 8045 which is causing the reported behaviour.

Port scans will establish a TCP connection. After the application related to the port, in this case XCOM, has sent the acknowledgement, the port scan software will close the TCP connection unconditionally. Depending on network and process timing, the closing of the TCP connection may or may not create an MCH0601 message.